Last week the museum removed three pieces from the exhibition “Art and China After 1989: Theater of the World” following pressure from animal-rights activists; countercriticism followed from artists, curators, and anti-censorship activists. Now Guggenheim director Richard Armstrong has explained his decision: “It was not only the quantity of people’s reactions, but there were a number of them that bordered on ominously threatening, or beyond that. We were obliged to consult with the police.”